Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
A detailed analysis of the bremsstrahlung spectrum at nonrelativistic electron scattering on argo... more A detailed analysis of the bremsstrahlung spectrum at nonrelativistic electron scattering on argon and xenon is carried out. It is shown that the approximate formulas widely used for the description of bremsstrahlung spectra lead to predictions that significantly differ from the exact results. In the limit when the photon frequency tends to zero, a rigorous proof of the relationship between the spectrum of the bremsstrahlung with a transport cross section of electron scattering on an atom is given. This proof does not require any assumptions about the dependence of the scattering phases on energy. For electron energies lower than the luminescence threshold, it is shown that the predictions for a number of radiated photons obtained by the exact formula are in good agreement with the available experimental data.
Determination of nuclear moments for many nuclei relies on the computation of hyperfine constants... more Determination of nuclear moments for many nuclei relies on the computation of hyperfine constants, with theoretical uncertainties directly affecting the resulting uncertainties of the nuclear moments. In this work we improve the precision of such method by including for the first time an iterative solution of equations for the core triple cluster amplitudes into the relativistic coupledcluster method, with large-scale complete basis sets. We carried out calculations of the energies and magnetic dipole and electric quadrupole hyperfine structure constants for the low-lying states of 229 Th 3+ in the framework of such relativistic coupled-cluster single double triple (CCSDT) method. We present a detailed study of various corrections to all calculated properties. Using the theory results and experimental data we found the nuclear magnetic dipole and electric quadrupole moments to be µ = 0.366(6)µN and Q = 3.11(2) eb, and reducing the uncertainty of the quadrupole moment by a factor of three. The Bohr-Weisskopf effect of the finite nuclear magnetization is investigated, with bounds placed on the deviation of the magnetization distribution from the uniform one.
In this letter we discuss how to include Breit interaction in calculations of low-energy properti... more In this letter we discuss how to include Breit interaction in calculations of low-energy properties of heavy atoms in accurate and effective way. In order to illustrate our approach we give some results for Cs and Tl.
Microwave and far infrared (FIR) spectra posses higher sensitivity to possible variation of funda... more Microwave and far infrared (FIR) spectra posses higher sensitivity to possible variation of fundamental constants, than optical and UV spectra. Molecular rotational lines and, particularly, inversion line of ammonia are sensitive to variation of proton-toelectron mass ratio, while fine-structure lines of C I, C II, N II, and O I, O III are sensitive to variation of fine-structure constant. Comparing apparent redshifts of these lines one can place stringent limits on time-variation of fundamental constants at extremely high redshifts, up to z~10.
We present an ab initio method of calculation of isotope shift in atoms with a few valence electr... more We present an ab initio method of calculation of isotope shift in atoms with a few valence electrons, based on the configuration-interaction calculation of energy. The main motivation for developing the method comes from the need to analyze whether differences in isotope abundance in early universe can contribute to the observed anomalies in quasar absorption spectra. The current best explanation for these anomalies is the assumption that the fine structure constant α was smaller at early epoch. We show that we can calculate the isotope shift in magnesium with good accuracy.
We propose using matrix-isolated paramagnetic diatomic molecules to search for the electric dipol... more We propose using matrix-isolated paramagnetic diatomic molecules to search for the electric dipole moment of electron (eEDM). As was suggested by Shapiro in 1968, the eEDM leads to a magnetization of a sample in the external electric field. In a typical condensed matter experiment, the effective field on the unpaired electron is of the same order of magnitude as the laboratory field, typically about 10 5 V/cm. We exploit the fact that the effective electric field inside heavy polar molecules is in the order of 10 10 V/cm. This leads to a huge enhancement of the Shapiro effect. Statistical sensitivity of the proposed experiment may allow one to improve the current limit on eEDM by three orders of magnitude in few hours accumulation time.
The Dirac–Hartree–Fock plus many-body perturbation theory (DHF + MBPT) method has been used to ca... more The Dirac–Hartree–Fock plus many-body perturbation theory (DHF + MBPT) method has been used to calculate hyperfine structure constants for Fr. Calculated hyperfine structure anomaly for hydrogen-like ion is in good agreement with analytical expressions. It has been shown that the ratio of the anomalies for s and p1/2 states is weakly dependent on the principal quantum number. Finally, we estimate Bohr–Weisskopf corrections for several Fr isotopes. Our results may be used to improve experimental accuracy for the nuclear g factors of short-lived isotopes.
The methanol molecule CH 3 OH has a complex microwave spectrum with a large number of very strong... more The methanol molecule CH 3 OH has a complex microwave spectrum with a large number of very strong lines. This spectrum includes purely rotational transitions as well as transitions with contributions of the internal degree of freedom associated with the hindered rotation of the OH group. The latter takes place due to the tunneling of hydrogen through the potential barriers between three equivalent potential minima. Such transitions are highly sensitive to changes in the electron-to-proton mass ratio, µ = m e /m p , and have different responses to µ-variations. The highest sensitivity is found for the mixed rotation-tunneling transitions at low frequencies. Observing methanol lines provides more stringent limits on the hypothetical variation of µ than ammonia observation with the same velocity resolution. We show that the best quality radio astronomical data on methanol maser lines constrain the variability of µ in the Milky Way at the level of |∆µ/µ| < 28 × 10 −9 (1σ) which is in line with the previously obtained ammonia result, |∆µ/µ| < 29 × 10 −9 (1σ). This estimate can be further improved if the rest frequencies of the CH 3 OH microwave lines will be measured more accurately.
Aims. We probe the dependence of the electron-to-proton mass ratio, μ = m e /m p , on the ambient... more Aims. We probe the dependence of the electron-to-proton mass ratio, μ = m e /m p , on the ambient matter density by means of radio astronomical observations. Methods. The ammonia method, which has been proposed to explore the electron-to-proton mass ratio, is applied to nearby dark clouds in the Milky Way. This ratio, which is measured in different physical environments of high (terrestrial) and low (interstellar) densities of baryonic matter is supposed to vary in chameleon-like scalar field models, which predict strong dependences of both masses and coupling constant on the local matter density. High resolution spectral observations of molecular cores in lines of NH 3 (J, K) = (1, 1), HC 3 N J = 2−1, and N 2 H + J = 1−0 were performed at three radio telescopes to measure the radial velocity offsets, ΔV ≡ V rot − V inv , between the inversion transition of NH 3 (1,1) and the rotational transitions of other molecules with different sensitivities to the parameter Δμ/μ ≡ (μ obs − μ lab)/μ lab. Results. The measured values of ΔV exhibit a statistically significant velocity offset of 23 ± 4 stat ± 3 sys m s −1. When interpreted in terms of the electron-to-proton mass ratio variation, this infers that Δμ/μ = (2.2 ± 0.4 stat ± 0.3 sys) × 10 −8. If only a conservative upper bound is considered, then the maximum offset between ammonia and the other molecules is |ΔV| ≤ 30 m s −1. This provides the most accurate reference point at z = 0 for Δμ/μ of |Δμ/μ| ≤ 3 × 10 −8 .
Calculations of transition energies between low-lying states of mercury atom are performed in the... more Calculations of transition energies between low-lying states of mercury atom are performed in the frame of combined CI/MBPT2 method. Results of all-electron relativistic calculations (using the Dirac-Coulomb Hamiltonian) are compared with experimental data and results of other four-component calculations. The results of the RECP calculations are compared with the corresponding all-electron results in order to estimate accuracy of different RECPs. Contributions from correlations in different shells to the calculated excitation energies as well as effects of basis set truncation at different orbital angular momenta, nuclear models, errors in gaussian approximation of the GRECP components are reported. Analysis of the obtained results shows that at least 34 external electrons of mercury atom should be correlated and the one-electron basis set should contain up to h angular momentum functions in order to reach a reliable agreement with experimental data within 200 cm −1. It is concluded that correlations of the 4f electrons can be efficiently taken into account for 20 electron GRECP at the generation stage. SHORT NAME: CI/MBPT2 calculations of mercury.
Journal of Experimental and Theoretical Physics Letters, 2002
We calculate nuclear spin-dependent parity non-conserving E1-amplitudes for optical transition 6p... more We calculate nuclear spin-dependent parity non-conserving E1-amplitudes for optical transition 6p 1/2,F → 6p 3/2,F ′ and for hyperfine transition 6p 1/2,F → 6p 1/2,F ′ in 205 Tl. Experimental limit on the former amplitude placed by Vetter et al. [PRL,74,2658 (1995)] corresponds to the anapole moment constant κa = −0.26 ± 0.27.
We show that three group IIIB divalent ions, B + , Al + , and In + , have anomalously small black... more We show that three group IIIB divalent ions, B + , Al + , and In + , have anomalously small blackbody radiation (BBR) shifts of the ns 2 1 S0 − nsnp 3 P o 0 clock transitions. The fractional BBR shifts for these ions are at least 10 times smaller than those of any other present or proposed optical frequency standards at the same temperature, and are less than 0.3% of the Sr clock shift. We have developed a hybrid configuration interaction + coupled-cluster method that provides accurate treatment of correlation corrections in such ions, considers all relevant states in the same systematic way, and yields a rigorous upper bound on the uncertainty of the final results. We reduce the BBR contribution to the fractional frequency uncertainty of the Al + clock to 4 × 10 −19 at T =300 K. We also reduce the uncertainties due to this effect at room temperature to 10 −18 level for B + and In + to facilitate further development of these systems for metrology and quantum sensing. These uncertainties approach recent estimates of the feasible precision of currently proposed optical atomic clocks.
We show that three group IIIB divalent ions, B + , Al + , and In + , have anomalously small black... more We show that three group IIIB divalent ions, B + , Al + , and In + , have anomalously small blackbody radiation (BBR) shifts of the ns 2 1 S0 − nsnp 3 P o 0 clock transitions. The fractional BBR shifts for these ions are at least 10 times smaller than those of any other present or proposed optical frequency standards at the same temperature, and are less than 0.3% of the Sr clock shift. We have developed a hybrid configuration interaction + coupled-cluster method that provides accurate treatment of correlation corrections in such ions, considers all relevant states in the same systematic way, and yields a rigorous upper bound on the uncertainty of the final results. We reduce the BBR contribution to the fractional frequency uncertainty of the Al + clock to 4 × 10 −19 at T =300 K. We also reduce the uncertainties due to this effect at room temperature to 10 −18 level for B + and In + to facilitate further development of these systems for metrology and quantum sensing. These uncertainties approach recent estimates of the feasible precision of currently proposed optical atomic clocks.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
A detailed analysis of the bremsstrahlung spectrum at nonrelativistic electron scattering on argo... more A detailed analysis of the bremsstrahlung spectrum at nonrelativistic electron scattering on argon and xenon is carried out. It is shown that the approximate formulas widely used for the description of bremsstrahlung spectra lead to predictions that significantly differ from the exact results. In the limit when the photon frequency tends to zero, a rigorous proof of the relationship between the spectrum of the bremsstrahlung with a transport cross section of electron scattering on an atom is given. This proof does not require any assumptions about the dependence of the scattering phases on energy. For electron energies lower than the luminescence threshold, it is shown that the predictions for a number of radiated photons obtained by the exact formula are in good agreement with the available experimental data.
Determination of nuclear moments for many nuclei relies on the computation of hyperfine constants... more Determination of nuclear moments for many nuclei relies on the computation of hyperfine constants, with theoretical uncertainties directly affecting the resulting uncertainties of the nuclear moments. In this work we improve the precision of such method by including for the first time an iterative solution of equations for the core triple cluster amplitudes into the relativistic coupledcluster method, with large-scale complete basis sets. We carried out calculations of the energies and magnetic dipole and electric quadrupole hyperfine structure constants for the low-lying states of 229 Th 3+ in the framework of such relativistic coupled-cluster single double triple (CCSDT) method. We present a detailed study of various corrections to all calculated properties. Using the theory results and experimental data we found the nuclear magnetic dipole and electric quadrupole moments to be µ = 0.366(6)µN and Q = 3.11(2) eb, and reducing the uncertainty of the quadrupole moment by a factor of three. The Bohr-Weisskopf effect of the finite nuclear magnetization is investigated, with bounds placed on the deviation of the magnetization distribution from the uniform one.
In this letter we discuss how to include Breit interaction in calculations of low-energy properti... more In this letter we discuss how to include Breit interaction in calculations of low-energy properties of heavy atoms in accurate and effective way. In order to illustrate our approach we give some results for Cs and Tl.
Microwave and far infrared (FIR) spectra posses higher sensitivity to possible variation of funda... more Microwave and far infrared (FIR) spectra posses higher sensitivity to possible variation of fundamental constants, than optical and UV spectra. Molecular rotational lines and, particularly, inversion line of ammonia are sensitive to variation of proton-toelectron mass ratio, while fine-structure lines of C I, C II, N II, and O I, O III are sensitive to variation of fine-structure constant. Comparing apparent redshifts of these lines one can place stringent limits on time-variation of fundamental constants at extremely high redshifts, up to z~10.
We present an ab initio method of calculation of isotope shift in atoms with a few valence electr... more We present an ab initio method of calculation of isotope shift in atoms with a few valence electrons, based on the configuration-interaction calculation of energy. The main motivation for developing the method comes from the need to analyze whether differences in isotope abundance in early universe can contribute to the observed anomalies in quasar absorption spectra. The current best explanation for these anomalies is the assumption that the fine structure constant α was smaller at early epoch. We show that we can calculate the isotope shift in magnesium with good accuracy.
We propose using matrix-isolated paramagnetic diatomic molecules to search for the electric dipol... more We propose using matrix-isolated paramagnetic diatomic molecules to search for the electric dipole moment of electron (eEDM). As was suggested by Shapiro in 1968, the eEDM leads to a magnetization of a sample in the external electric field. In a typical condensed matter experiment, the effective field on the unpaired electron is of the same order of magnitude as the laboratory field, typically about 10 5 V/cm. We exploit the fact that the effective electric field inside heavy polar molecules is in the order of 10 10 V/cm. This leads to a huge enhancement of the Shapiro effect. Statistical sensitivity of the proposed experiment may allow one to improve the current limit on eEDM by three orders of magnitude in few hours accumulation time.
The Dirac–Hartree–Fock plus many-body perturbation theory (DHF + MBPT) method has been used to ca... more The Dirac–Hartree–Fock plus many-body perturbation theory (DHF + MBPT) method has been used to calculate hyperfine structure constants for Fr. Calculated hyperfine structure anomaly for hydrogen-like ion is in good agreement with analytical expressions. It has been shown that the ratio of the anomalies for s and p1/2 states is weakly dependent on the principal quantum number. Finally, we estimate Bohr–Weisskopf corrections for several Fr isotopes. Our results may be used to improve experimental accuracy for the nuclear g factors of short-lived isotopes.
The methanol molecule CH 3 OH has a complex microwave spectrum with a large number of very strong... more The methanol molecule CH 3 OH has a complex microwave spectrum with a large number of very strong lines. This spectrum includes purely rotational transitions as well as transitions with contributions of the internal degree of freedom associated with the hindered rotation of the OH group. The latter takes place due to the tunneling of hydrogen through the potential barriers between three equivalent potential minima. Such transitions are highly sensitive to changes in the electron-to-proton mass ratio, µ = m e /m p , and have different responses to µ-variations. The highest sensitivity is found for the mixed rotation-tunneling transitions at low frequencies. Observing methanol lines provides more stringent limits on the hypothetical variation of µ than ammonia observation with the same velocity resolution. We show that the best quality radio astronomical data on methanol maser lines constrain the variability of µ in the Milky Way at the level of |∆µ/µ| < 28 × 10 −9 (1σ) which is in line with the previously obtained ammonia result, |∆µ/µ| < 29 × 10 −9 (1σ). This estimate can be further improved if the rest frequencies of the CH 3 OH microwave lines will be measured more accurately.
Aims. We probe the dependence of the electron-to-proton mass ratio, μ = m e /m p , on the ambient... more Aims. We probe the dependence of the electron-to-proton mass ratio, μ = m e /m p , on the ambient matter density by means of radio astronomical observations. Methods. The ammonia method, which has been proposed to explore the electron-to-proton mass ratio, is applied to nearby dark clouds in the Milky Way. This ratio, which is measured in different physical environments of high (terrestrial) and low (interstellar) densities of baryonic matter is supposed to vary in chameleon-like scalar field models, which predict strong dependences of both masses and coupling constant on the local matter density. High resolution spectral observations of molecular cores in lines of NH 3 (J, K) = (1, 1), HC 3 N J = 2−1, and N 2 H + J = 1−0 were performed at three radio telescopes to measure the radial velocity offsets, ΔV ≡ V rot − V inv , between the inversion transition of NH 3 (1,1) and the rotational transitions of other molecules with different sensitivities to the parameter Δμ/μ ≡ (μ obs − μ lab)/μ lab. Results. The measured values of ΔV exhibit a statistically significant velocity offset of 23 ± 4 stat ± 3 sys m s −1. When interpreted in terms of the electron-to-proton mass ratio variation, this infers that Δμ/μ = (2.2 ± 0.4 stat ± 0.3 sys) × 10 −8. If only a conservative upper bound is considered, then the maximum offset between ammonia and the other molecules is |ΔV| ≤ 30 m s −1. This provides the most accurate reference point at z = 0 for Δμ/μ of |Δμ/μ| ≤ 3 × 10 −8 .
Calculations of transition energies between low-lying states of mercury atom are performed in the... more Calculations of transition energies between low-lying states of mercury atom are performed in the frame of combined CI/MBPT2 method. Results of all-electron relativistic calculations (using the Dirac-Coulomb Hamiltonian) are compared with experimental data and results of other four-component calculations. The results of the RECP calculations are compared with the corresponding all-electron results in order to estimate accuracy of different RECPs. Contributions from correlations in different shells to the calculated excitation energies as well as effects of basis set truncation at different orbital angular momenta, nuclear models, errors in gaussian approximation of the GRECP components are reported. Analysis of the obtained results shows that at least 34 external electrons of mercury atom should be correlated and the one-electron basis set should contain up to h angular momentum functions in order to reach a reliable agreement with experimental data within 200 cm −1. It is concluded that correlations of the 4f electrons can be efficiently taken into account for 20 electron GRECP at the generation stage. SHORT NAME: CI/MBPT2 calculations of mercury.
Journal of Experimental and Theoretical Physics Letters, 2002
We calculate nuclear spin-dependent parity non-conserving E1-amplitudes for optical transition 6p... more We calculate nuclear spin-dependent parity non-conserving E1-amplitudes for optical transition 6p 1/2,F → 6p 3/2,F ′ and for hyperfine transition 6p 1/2,F → 6p 1/2,F ′ in 205 Tl. Experimental limit on the former amplitude placed by Vetter et al. [PRL,74,2658 (1995)] corresponds to the anapole moment constant κa = −0.26 ± 0.27.
We show that three group IIIB divalent ions, B + , Al + , and In + , have anomalously small black... more We show that three group IIIB divalent ions, B + , Al + , and In + , have anomalously small blackbody radiation (BBR) shifts of the ns 2 1 S0 − nsnp 3 P o 0 clock transitions. The fractional BBR shifts for these ions are at least 10 times smaller than those of any other present or proposed optical frequency standards at the same temperature, and are less than 0.3% of the Sr clock shift. We have developed a hybrid configuration interaction + coupled-cluster method that provides accurate treatment of correlation corrections in such ions, considers all relevant states in the same systematic way, and yields a rigorous upper bound on the uncertainty of the final results. We reduce the BBR contribution to the fractional frequency uncertainty of the Al + clock to 4 × 10 −19 at T =300 K. We also reduce the uncertainties due to this effect at room temperature to 10 −18 level for B + and In + to facilitate further development of these systems for metrology and quantum sensing. These uncertainties approach recent estimates of the feasible precision of currently proposed optical atomic clocks.
We show that three group IIIB divalent ions, B + , Al + , and In + , have anomalously small black... more We show that three group IIIB divalent ions, B + , Al + , and In + , have anomalously small blackbody radiation (BBR) shifts of the ns 2 1 S0 − nsnp 3 P o 0 clock transitions. The fractional BBR shifts for these ions are at least 10 times smaller than those of any other present or proposed optical frequency standards at the same temperature, and are less than 0.3% of the Sr clock shift. We have developed a hybrid configuration interaction + coupled-cluster method that provides accurate treatment of correlation corrections in such ions, considers all relevant states in the same systematic way, and yields a rigorous upper bound on the uncertainty of the final results. We reduce the BBR contribution to the fractional frequency uncertainty of the Al + clock to 4 × 10 −19 at T =300 K. We also reduce the uncertainties due to this effect at room temperature to 10 −18 level for B + and In + to facilitate further development of these systems for metrology and quantum sensing. These uncertainties approach recent estimates of the feasible precision of currently proposed optical atomic clocks.
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Papers by Mikhail Kozlov